code: def metric_func(self):
      self._metric_func = {"Cmiou": max, "Imiou": max, "loss": min}
      return self._metric_func
  
file_path: torch-points3d/torch_points3d/metrics/shapenet_part_tracker.py
imports: import numpy
  from .confusion_matrix import ConfusionMatrix
  from .base_tracker import meter_value, BaseTracker
  from torch_geometric.data import Data
  from torch_points3d.models import model_interface
  from torch_points3d.core.data_transform import SaveOriginalPosId
  from torch_points3d.metrics.segmentation_helpers import SegmentationVoter
label_desc: Use image node_id 8 for calling the ShapenetPartTracker obj's underlying member method code with example usage: obj.metric_func() and returns: self